package com.example.demo.utils;

/**
 * @author Lucy
 * @create 2024-02-01 15:21
 */

import java.io.*;
import java.util.Base64;

/**
 * Base64 工具类
 */
public class Base64Util {
    private static final char last2byte = (char) Integer.parseInt("00000011", 2);
    private static final char last4byte = (char) Integer.parseInt("00001111", 2);
    private static final char last6byte = (char) Integer.parseInt("00111111", 2);
    private static final char lead6byte = (char) Integer.parseInt("11111100", 2);
    private static final char lead4byte = (char) Integer.parseInt("11110000", 2);
    private static final char lead2byte = (char) Integer.parseInt("11000000", 2);
    private static final char[] encodeTable = new char[]{'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'};

    public Base64Util() {
    }

    public static String encode(byte[] from) {
        StringBuilder to = new StringBuilder((int) ((double) from.length * 1.34D) + 3);
        int num = 0;
        char currentByte = 0;

        int i;
        for (i = 0; i < from.length; ++i) {
            for (num %= 8; num < 8; num += 6) {
                switch (num) {
                    case 0:
                        currentByte = (char) (from[i] & lead6byte);
                        currentByte = (char) (currentByte >>> 2);
                    case 1:
                    case 3:
                    case 5:
                    default:
                        break;
                    case 2:
                        currentByte = (char) (from[i] & last6byte);
                        break;
                    case 4:
                        currentByte = (char) (from[i] & last4byte);
                        currentByte = (char) (currentByte << 2);
                        if (i + 1 < from.length) {
                            currentByte = (char) (currentByte | (from[i + 1] & lead2byte) >>> 6);
                        }
                        break;
                    case 6:
                        currentByte = (char) (from[i] & last2byte);
                        currentByte = (char) (currentByte << 4);
                        if (i + 1 < from.length) {
                            currentByte = (char) (currentByte | (from[i + 1] & lead4byte) >>> 4);
                        }
                }

                to.append(encodeTable[currentByte]);
            }
        }

        if (to.length() % 4 != 0) {
            for (i = 4 - to.length() % 4; i > 0; --i) {
                to.append("=");
            }
        }

        return to.toString();
    }

    /**
     * 将Base64编码的字符串转换为图片并保存到指定的文件路径。
     *
     * @param base64String Base64编码的字符串
     * @param filePath     要保存的图片文件路径
     * @return true 如果转换成功，否则返回false
     */
    public static boolean base64ToImage(String base64String, String filePath) {
        try (FileOutputStream fileOutputStream = new FileOutputStream(filePath)) {
            // Base64解码
            byte[] imageBytes = Base64.getDecoder().decode(base64String);
            // 将字节数组写入文件
            fileOutputStream.write(imageBytes);
            return true;
        } catch (IOException e) {
            e.printStackTrace();
        }
        return false;
    }

    /**
     * 将Base64编码的字符串转换为字节数组
     *
     * @param base64String Base64编码的字符串
     * @return byte[] 返回字节数组
     */
    public static byte[] base64ToBytes(String base64String) {
        // 删除Base64字符串中的URL安全字符，如果有的话
        base64String = base64String.replace('-', '+').replace('_', '/');
        // 确保Base64字符串的长度是4的倍数，如果不是则填充'='字符直到它是
        int mod4 = base64String.length() % 4;
        if (mod4 > 0) {
            base64String += "====".substring(mod4);
        }
        // 解码Base64字符串到字节数组
        return Base64.getDecoder().decode(base64String);
    }
    /**
     * 将图片地址转换为Base64编码
     *
     * @param filePath 图片地址
     * @return base64Image 图片转成的base64编码
     */
    public static String convertImageToBase64(String filePath) {
        File file = new File(filePath);
        try (InputStream inputStream = new FileInputStream(file)) {
            byte[] bytes = new byte[(int) file.length()];
            inputStream.read(bytes);

            // 对图片进行Base64编码
            String base64Image = Base64.getEncoder().encodeToString(bytes);
            return base64Image;
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }
}
